Oxygen storage management and control with three-way catalyst

• US 6,715,281 B2
• Filed: 08/28/2002
• Issued: 04/06/2004
• Est. Priority Date: 08/28/2002
• Status: Active Grant

• Current Assignee: FCA US LLC (Stellantis NV)
• Original Assignee: Daimler Chrysler Corporation (Mercedes-Benz Group AG)
• Inventors: Zhu, Dannie
• Primary Examiner(s): Denion, Thomas
• Assistant Examiner(s): NGUYEN, TU MINH
• Application Number:
  US10/232,784
• Publication Number:
  US 20040040282A1
• Time in Patent Office: 587 Days
• Field of Search: 602/74, 602/76, 602/77, 602/85, 73/233.1, 73/233.2, 731/181
• US Class Current: 60/276
• CPC Class Codes: F02D 2200/0814 Oxygen storage amount
• CPC Class Codes: F02D 2200/0816 Oxygen storage capacity
• CPC Class Codes: F02D 41/0295 Control according to the amount of oxygen that is stored on the exhaust gas treating apparatus
• CPC Class Codes: F02D 41/1441 Plural sensors

Abstract

A method and system for controlling exhaust emissions from an engine of a motor vehicle includes sensing oxygen levels upstream and downstream of a catalytic converter, predicting an instantaneous oxygen storage amount in the catalytic converter, determining a maximum oxygen storage capacity, selecting a target percentage of the maximum oxygen storage amount, and controlling the motor vehicle engine performance to a state where the oxygen storage amount is approximately the target percentage of the maximum oxygen storage amount. The instantaneous oxygen storage amount is determined from an oxygen storage mass flow rate, which is determined from a converter-in mass flow rate, converter-out mass flow rate, and a predicted oxygen consumption mass flow rate. The converter-in and converter-out mass flow rates are calculated from an upstream and downstream oxygen mass fraction, respectively, based on the sensed upstream and downstream oxygen levels, respectively.

Claims

1. A method of controlling exhaust emissions in a motor vehicle having an engine control system and a catalytic converter, the steps comprising:

sensing an oxygen level upstream of a catalytic converter;

sensing an oxygen level downstream of the catalytic converter;

predicting an oxygen consumption mass flow rate, said oxygen consumption mass flow rate including oxygen consumed, but not stored, within the catalytic converter;

determining an oxygen storage mass flow rate based on said steps of sensing said upstream and downstream oxygen level and said predicted oxygen consumption mass flow rate; and

determining an instantaneous oxygen storage amount from said oxygen storage mass flow rate.

2. The method according to claim 1, further comprising the steps of:

calculating an upstream oxygen mass fraction from said sensed upstream oxygen level; and

calculating a downstream oxygen mass fraction from said sensed downstream oxygen level;

wherein said calculated upstream and downstream oxygen mass fractions are used to determine said oxygen storage mass flow rate.

3. The method according to claim 2, further comprising the step of calculating a converter-in oxygen mass flow rate and a converter-out oxygen mass flow rate from said upstream oxygen mass fraction and said downstream oxygen mass fraction.

4. The method according to claim 3, wherein said step of determining an oxygen storage mass flow rate is determined from said converter-in oxygen mass flow rate, converter-out oxygen mass flow rate, and said predicted oxygen consumption mass flow rate.

5. The method according to claim 3, further comprising the step of determining an upstream lambda by determining an upstream oxygen flow rate from said step of sensing an oxygen level upstream of the catalytic converter.

6. The method according to claim 5, further comprising the step of determining a downstream lambda by determining a downstream oxygen flow rate from said step of sensing an oxygen level downstream of the catalytic converter.

7. The method according to claim 6, wherein said step of determining said upstream oxygen mass fraction uses said upstream lambda, a set of reaction constants, and a reaction fraction.

8. The method according to claim 7, wherein said step of determining said downstream oxygen mass fraction is achieved by using said downstream lambda, a set of reaction constants, and a reaction fraction.

9. An engine control system for a motor vehicle having an engine with an exhaust coupled to a catalytic converter, the control system comprising:

an upstream oxygen sensor disposed upstream from the catalytic converter;

a downstream oxygen sensor disposed downstream from the catalytic converter;

an engine controller monitoring engine operating parameters, monitoring output signals of said upstream and downstream oxygen sensors, determining an amount of oxygen consumed within the catalytic converter upstream of said downstream oxygen sensor, determining an amount of oxygen stored in the catalytic converter based on said monitored sensor output signals and said amount of oxygen consumed, and controlling engine operation to maintain said oxygen storage amount within an oxygen storage capacity of the catalytic converter.

10. The engine control system of claim 9, wherein said engine controller further includes a target oxygen storage amount selected within a range from zero oxygen storage capacity to about said oxygen storage capacity, and said engine controller controlling engine operation to maintain said amount of oxygen stored in the catalytic converter at approximately said target oxygen storage amount.

11. The engine control system of claim 10, wherein a plurality of fuel injectors receive a control signal from said engine controller to supply fuel to the engine at a rate where said oxygen storage amount is approximately said target oxygen storage amount.

12. A method of controlling exhaust emissions from a catalytic converter connected to the exhaust of a motor vehicle engine, the steps comprising:

sensing an oxygen level upstream of the catalytic converter,

sensing an oxygen level downstream of the catalytic converter;

predicting an oxygen consumption mass flow rate;

determining an oxygen storage mass flow rate based on said steps of sensing said upstream and downstream oxygen levels and said predicted oxygen consumption mass flow rate;

determining an instantaneous oxygen storage amount from oxygen storage mass flow rate;

determining a maximum oxygen storage capacity;

selecting a target percentage of said maximum oxygen storage amount; and

controlling the motor vehicle engine performance to a state where said predicted instantaneous oxygen storage amount is approximately said target percentage of said maximum oxygen storage amount.

13. The method according to claim 12, further comprising the step of determining an upstream oxygen flow rate from said step of sensing an oxygen level upstream of the catalytic converter.

14. The method according to claim 12, further comprising the step of determining a downstream oxygen flow rate from said step of sensing an oxygen level downstream of the catalytic converter.

15. The method according to claim 12, further comprising the steps of:

calculating an upstream oxygen mass fraction from said sensed upstream oxygen level; and

calculating a downstream oxygen mass fraction from said sensed downstream oxygen level;

wherein said calculated upstream and downstream oxygen mass fractions are used to determine said oxygen storage mass flow rate.

16. The method according to claim 15, wherein said step of determining said upstream oxygen mass fraction further comprises using a set of reaction constants, a reaction fraction, and a determined upstream lambda.

17. The method according to claim 15, wherein said step of determining said downstream oxygen mass fraction further comprises using a set of reaction constants, a reaction fraction, and a determined downstream lambda.

18. The method according to claim 15, further comprising the step of calculating a converter-in oxygen mass flow rate and a converter-out oxygen mass flow rate from said upstream oxygen mass fraction and said downstream oxygen mass fraction.

19. The method according to claim 18, wherein said step of determining an oxygen storage mass flow rate is determined from said converter-in oxygen mass flow rate, converter-out oxygen mass flow rate, and said predicted oxygen consumption mass flow rate.